Direct-conversion receiver system and method with quadrature balancing and DC offset removal

ABSTRACT

A system and method are provided for direct-conversion of a modulated radio-frequency (RF) signal. After receiving an RF signal, the RF signal is mixed with a plurality of oscillator signals with different phases in an interleaving manner.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/807,208, filed Mar. 22, 2004, which claims the benefit of priorityunder 35 U.S.C. 119(e) to provisional U.S. Patent Application No.60/456,510 filed Mar. 24, 2003, all of which are incorporated herein byreference in their entirety.

FIELD OF THE INVENTION

The present invention relates to circuitry, and more particularly todirect-conversion circuitry.

BACKGROUND OF THE INVENTION

Direct-conversion is a wireless receiver architecture particularlysuited to highly integrated, low-power terminals. Its advantage overtraditional superheterodyne architectures is that the received signal isamplified and filtered at baseband rather than at some higherintermediate frequency. This architecture results in lower currentconsumption in the baseband circuitry and a simpler frequency plan.

In direct-conversion receivers, the most serious drawback is that thedirect current (DC) offset generated by the down-conversion mixers andbaseband circuitry. This offset appears in the middle of the downconverted signal spectrum, corrupting the signal.

The first cause of DC offset is the transistor mismatch of the basebandcomponents such as the down-conversion mixers and buffers. This isstatic DC offset. In addition, there is dynamic DC offset. One source ofdynamic DC offset occurs when the local oscillator (LO) leaks into thefront end of the receiver through the integrated circuit substrate. Thissignal is down converted to DC. Another source of dynamic DC offsetoccurs when the LO leaks out the antenna and reflects off externalobjects and back into the receiver. This too is down converted to DC.

DC offsets may be removed through capacitive coupling if the signalmodulation is tolerant to the phase distortion cause bycapacitor-resistor (CR) coupling. In addition, DC offsets may beestimated and digitally removed at the cost of additional hardware sizeand complexity.

Another problem in direct-conversion receivers is in-phase andquadrature (“IQ”) imbalance of the LO and receiver. In the art, it iswell known that direct-conversion transmitter and receivers need a localoscillator with quadrature outputs for vector modulation anddemodulation. However, when the quadrature outputs are not equal inamplitude and not exactly 90 degrees out of phase, demodulation becomesmore difficult requiring a higher signal-to-noise ratio to properlydecode the signal.

Quadrature phases are typically derived by passing a reference localoscillator through a CR-RC phase shift network. Ideally, this createstwo signals with equal amplitude and 90 degrees of phase difference.However, this depends on the accuracy of resistors and capacitors whichmake up the phase shift network. The resistors and capacitors can varyby up to 15 percent in a typical integrated circuit causing the in-phaseand quadrature components to have different amplitudes and a phasedifference not equal to 90 degrees.

In addition, layout differences between the in-phase and quadraturepaths can cause additional amplitude/phase imbalance. Contributing tofurther in-phase/quadrature imbalance is the circuits in the in-phaseand quadrature paths, such as amplifiers and mixers, the physicalproperties of which differ slightly. Many feedback calibration schemeshave been proposed and implemented to mitigate quadrature imbalance atthe cost of hardware and/or system complexity.

In addition to DC offset and quadrature imbalance, radio-frequency (RF)integrated circuits suffer from self-generated interference.Specifically, signals from one part of the integrated circuit couple toanother part of the integrated circuit. The RF section of an integratedcircuit is the most susceptible portion since the received signal hasnot been fully amplified. One way to combat this problem is to turn thesignal from single-ended to differential. A differential signal iscomprised of a negative and a positive component. This adds to thesignal's resilience to self interference.

A conventional direct-conversion receiver is illustrated in FIG. 1. Asillustrated in FIG. 1, a direct-conversion receiver takes an RF signal10 characterized by a modulation bandwidth and a center frequency. TheLO produces a sinusoidal signal which has the same frequency as the RFsignal center frequency, as is typical for direct-conversion receivers.As an example, a Bluetooth™. signal might be transmitted at 2440 MHztherefore the LO may produce a 2440 MHz sinusoidal signal for downconversion.

Furthermore, the receiver multiplies the RF signal not with one but withtwo different phases 11, 12 of the LO. The two phases 11, 12 of thelocal oscillator are 90 degrees apart and thus, are known as thein-phase (I) 11 and quadrature (Q) 12 components. Through thisdisclosure, the in-phase local oscillator signal is denoted LO_(I) andthe quadrature local oscillator signal is denoted LO_(Q). The mixeroutputs 13, 14 are known as baseband signals since they are at a lowerfrequency than the RF signal. The baseband signals are in-phase andquadrature corresponding to the in-phase and quadrature local oscillatorsignals. The baseband signals are low pass filtered as to removeunwanted interfering signals. Through this disclosure, the in-phasebaseband signal is denoted BB_(I) and the quadrature baseband signal isdenoted BB_(Q). The resulting filtered baseband signals 15, 16 can berepresented by Equations 1 and 2.BB _(I) =RF×LO _(I)  Equation 1BB _(Q) =RF×LO _(Q)  Equation 2

Another conventional direct-conversion architecture is shown in FIG. 2.This differential direct-conversion architecture is more resilient toself-generated noise than the one illustrated in FIG. 1. In FIG. 2, theRF input signal 200 is converted by a balun 220 to a differential signalcomposed of positive and negative components 201, 202 respectively. Therelationship between the RF input 200 and the differential components201, 202 are described by Equation 3.RF=(RF _(pos) −RF _(neg))  Equation 3

Similarly, the differential direct-conversion architecture shown in FIG.2 uses differential LO signals to mix the RF signal down to baseband.The polyphase network 205 is a circuit which converts the localoscillator's voltage waveform 203 into four voltage waveforms 206, 207,208, 209 at the same frequency as the LO 203 but at 0, 180, 90, 270degrees offset compared to the LO signal 203 respectively.

Collectively, these four signals 206, 207, 208, 209 are referred to aspolyphase local oscillator signals. To facilitate the description ofthis embodiment, these signals are denoted 206, 207, 208, 209 as LO⁰,LO¹⁸⁰, LO⁹⁰, LO²⁷⁰ corresponding to their phase shift compared to thelocal oscillator 203. It is well known in the art that shifting asinusoidal signal 180 degrees in phase is the same as inverting thesignal. Therefore, the equivalent single-ended in-phase and quadratureLO signals are described mathematically as in Equations 4 and 5.LO _(I) =LO ⁰ −LO ¹⁸⁰  Equation 4LO _(Q) =LO ⁹⁰ −LO ²⁷⁰  Equation 5

The differential RF signal 201, 202 is then routed to the differentialmixers 210, 211 where it is multiplied by the differential localoscillator signals. At the first mixer 210, the differential RF signalis multiplied by the in-phase LO (LO_(I)) to generate the differentialin-phase baseband signal 212, 213 (BB_(I)). Likewise, at the secondmixer 211, the differential RF signal is multiplied by the quadrature LO(LO_(Q)) to generate the differential quadrature baseband signal 214,215 (BB_(Q)). Equations 6 and 7 describe the mixing process of thedifferential signals to generate the BB_(I) and the BB_(Q).BB _(I)=(BB _(I,pos) −BB _(I,neg))=(RF _(POS) −RF _(neg))×(LO ⁰ −LO¹⁸⁰)  Equation 6BB _(Q)=(BB _(Q,pos) −BB _(Q,neg))=(RF _(pos) −RF _(neg))×(LO ⁹⁰ −LO²⁷⁰)  Equation 7

As in the single-ended case, the baseband signals 212, 213, 214, 215 canbe filtered to remove unwanted interfering signals to produce filteredbaseband signals 216, 217, 218, 219.

Now, to elucidate the problems with direct-conversion receivers, DCoffset and imbalance distortions will be added to Equations 6 and 7. DCoffsets are added to the output of the mixers. DC 1 represents thedifferential DC offset of the first mixer 210 and DC2 represents thedifferential DC offset of the second mixer 211. Likewise the amplitudeand phase imbalance of the mixers and the polyphase LO signals can beaccounted for at the output of each mixer. A complex multiplicativeterm, A1e^(jP1), represents a random amplitude variation (A1) and arandom phase variation (P1) introduced by the first mixer 210 and thesignal path and LO path connected to the mixer. Likewise, A2e^(P2)represents a random amplitude and phase variation introduced by thesecond mixer 211 and the signal and LO paths connected thereto. Thus,with these distortions added, Equations 6 and 7 become Equations 11 and12.BB _(I)=(RF _(pos) −RF _(neg))×(LO ⁰ −LO ¹⁸⁰)×A1e ^(jP1) +DC1  Equation11BB _(Q)=(RF _(pos) −RF _(neg))×(LO ⁹⁰ −LO ²⁷⁰)×A2e ^(jP2) +DC2  Equation12

As seen in Equations 11 and 12, the baseband in-phase and quadraturesignals imbalance grows as A1 and A2 differ and as P1 and P2 differ. Asthe imbalance increases, it is harder for the signal to be received anddecoded. Likewise, as DC1 and DC2 get larger, and thus depart from theideal of no DC offset, it becomes more difficult for the signal to bereceived and decoded.

SUMMARY OF THE INVENTION

A system and method are provided for direct-conversion of a modulatedradio-frequency (RF) signal. After receiving an RF signal, the RF signalis mixed with a plurality of oscillator signals with different phases inan interleaving manner.

In one embodiment, the RF signal may be converted to a differential RFsignal. Further, the RF signal may be modulated over a finite bandwidth.

In another embodiment, the oscillator signals may include an oscillatorsignal frequency substantially equal to an RF signal frequency of the RFsignal. Optionally, the oscillator signals may have phase differences of0, 90, 180 and 270 degrees.

In still another embodiment, the mixing may be carried out by aplurality of mixers. Further, the oscillator signals may be input to themixers in the interleaving manner. For example, the oscillator signalsmay be input to the mixers in the interleaving manner by switching whichoscillator signals are input to which mixers.

As an option, such switching may occur at a rate that is faster than abandwidth of the RF signal. Further, the switching may occur in asubstantially random manner, or even in a completely random manner.

In still yet another embodiment, a modulation of the RF signal may bereconstructed as a quadrature baseband signal and an in-phase basebandsignal with a de-interleaving operation. Optionally, suchde-interleaving operation may include inverting and routing operations.

Still yet, low-pass filtering may be applied to the in-phase basebandsignal and the quadrature baseband signal.

In use, a direct current (DC) offset of the in-phase baseband signal andthe quadrature baseband signal may thus be removed. Further, anamplitude and a phase distortion in the in-phase baseband signal and thequadrature baseband signal may be equated or reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a conventional single-endeddirect-conversion receiver, in accordance with the prior art.

FIG. 2 is a block diagram of a conventional differentialdirect-conversion receiver, in accordance with the prior art.

FIG. 3 is a block diagram of a differential direct-conversion receiverwith local-oscillator phase interleaving and baseband de-interleaving,in accordance with one embodiment.

FIGS. 4 a-d show the four configurations of the local-oscillator phaseinterleaver of FIG. 3.

FIGS. 5 a-d show the four configurations of the baseband de-interleaverof FIG. 3.

FIG. 6 is an illustration of a wireless communication system in whichone embodiment may be used.

FIG. 7 illustrates the functional components of a wireless communicationdevice, shown in block diagram format.

DETAILED DESCRIPTION OF THE INVENTION

Turning to one embodiment in FIG. 3, a differential direct-conversionarchitecture and associated method are provided with two switchingmatrices: 1) the local oscillator phase interleaver (LOPI) 310 circuit,and 2) the baseband de-interleaver (BBDI) 330. Each has fourcombinations of connections. The four combinations of LOPI areillustrated in FIGS. 4 a, 4 b, 4 c and 4 d. In keeping with theterminology established in the previous example, the polyphase LOsignals 306, 307, 308, 309 are denoted: LO⁰, LO⁹⁰, LO¹⁸⁰, LO²⁷⁰.

To establish additional notation to unify the description the signals inFIG. 3 and FIG. 4, in FIG. 3 the positive input 313 to the first mixer341 will be denote M1+ in FIG. 4. Likewise, in FIG. 3 the negative input314 to the first mixer 341 will be denoted M1− in FIG. 4. Likewise, inFIG. 3 the positive input 315 to the second mixer 340 will be denotedM2+ in FIG. 4. Likewise, in FIG. 3 the negative input 316 to the secondmixer 340 will be denoted M2− in FIG. 4.

In state 1 as illustrated in FIG. 4 a, the local oscillator phaseinterleaver passes LO⁰, LO⁸⁰, LO⁹⁰, LO²⁷⁰ through to M1+, M1−, M2+, M2−respectively. In the second state as illustrated in FIG. 4 b, the LOphase interleaver routes LO¹⁸⁰, LO⁰, LO²⁷⁰, LO⁹⁰ through to M1+, M1−,M2+, M2− respectively. In state 3 as illustrated in FIG. 4 c, LO⁹⁰,LO²⁷⁰, LO⁰, LO¹⁸⁰ are routed to M1+, M1−, M2+, M2− respectively. Finallyin state 4 as illustrated in FIG. 4 d, LO²⁷⁰, LO⁹⁰, LO¹⁸⁰, LO⁰ arerouted to M1+, M1−, M2+, M2− respectively.

Through this method, each mixer input sees each polyphase LO signal LO⁰,LO⁹⁰, LO¹⁸⁰, LO²⁷⁰. Thus, if a phase or amplitude imbalance of one mixerdistorts one LO component then it distorts all components. For the fourstates, the output of the first mixer 341 is described by Equations 13,14, 15 and 16, and the output of the second mixer 340 is described byEquations 17, 18, 19, and 20.State 1: (RF _(pos) −RF _(neg))×(LO ⁰ −LO ¹⁸⁰)×A1e ^(jP1) +DC1  Equation13State 2: (RF _(pos) −RF _(neg))×(LO ¹⁸⁰ −LO ⁰)×A1e ^(jP1) +DC1  Equation14State 3: (RF _(pos) −RF _(neg))×(LO ⁹⁰ −LO ²⁷⁰)×A1e ^(jP1)+DC1  Equation 15State 4: (RF _(pos) −RF _(neg))×(LO ²⁷⁰ −LO ⁹⁰)×A1e ^(jP1)+DC1  Equation 16State 1: (RF _(pos) −RF _(neg))×(LO ⁹⁰ −LO ²⁷⁰)×A1e ^(jP2)+DC2  Equation 17State 2: (RF _(pos) −RF _(neg))×(LO ²⁷⁰ −LO ⁹⁰)×A1e ^(jP2)+DC2  Equation 18State 3: (RF _(pos) −RF _(neg))×(LO ⁰ −LO ¹⁸⁰)×A1e ^(jP2) +DC2  Equation19State 4: (RF _(pos) −RF _(neg))×(LO ¹⁸⁰ −LO ⁰)×A1e ^(jP2) +DC2  Equation20

In the context of the present description, “interleaving” may refer tothe plain and ordinary meaning thereof, as well as any sort ofswitching, exchanging, toggling, swapping, interchanging, etc.

The BBDI 330 undoes the interleaving that the LOPI introduced. Thebaseband de-interleaver 330 circuit interleaves between one of fourcombinations of connections illustrated in FIGS. 5 a-d. In addition, intwo of the states it inverts the incoming signal. To clarify thecorresponding notations between FIG. 3 and FIG. 5, in FIG. 3 thepositive output 317 of the first mixer 341 corresponds to the notationB1 in FIG. 5. Likewise, in FIG. 3 the negative output 318 of the firstmixer 341 corresponds to the notation B2 in FIG. 5. Likewise, in FIG. 3the positive output 319 of the second mixer 340 corresponds to thenotation B3 in FIG. 5. Likewise, in FIG. 3 the negative output 320 ofthe second mixer 340 corresponds to the notation B4 in FIG. 5.

To further clarify the corresponding notations between FIG. 3 and FIG.5, in FIG. 3 the positive in-phase baseband input 332 to the first lowpass filter 342 corresponds to the notation B5 in FIG. 5. Likewise, inFIG. 3 negative in-phase baseband input 333 to the first low pass filter342 corresponds to the notation B6 in FIG. 5. Likewise, in FIG. 3positive quadrature baseband 334 input to the second low pass filter 343corresponds to the notation B7 in FIG. 5. Likewise, in FIG. 3 negativequadrature baseband input to the second low pass filter 342 correspondsto the notation B8 in FIG. 5.

In state 1 illustrated in FIG. 5 a, the baseband de-interleaver passesB1, B2, B3, B4 through to B5, B6, B7, B8 respectively. In the secondstate illustrated in FIG. 5 b, the baseband de-interleaver inverts theincoming signals and routes B1, B2, B3, B4 to B5, B6, B7, B8respectively. In state 3 illustrated in FIG. 5 c, B3, B4, B1, B2 arerouted to B5, B6, B7, B8 respectively. Finally, in state 4 illustratedin FIG. 5 d, the baseband de-interleaver inverts the incoming signalsand routes B3, B4, B1, B2 to B5, B6, B7, B8 respectively.

Returning to FIG. 3, the in-phase baseband signal is comprised ofdifferential signals 332, 333. Likewise the quadrature baseband signalis comprised of differential signals 334, 335. For the four-states, thein-phase baseband signal is described by Equations 21, 22, 23, and 24.Likewise, the quadrature baseband signal is described by Equations 25,26, 27, and 28.State 1: (RF _(pos) −RF _(neg))×(LO ⁰ −LO ¹⁸⁰)×A1e ^(jP1) +DC1  Equation21State 2: (RF _(pos) −RF _(neg))×(LO ⁰ −LO ¹⁸⁰)×A1e ^(jP1) +DC1  Equation22State 3: (RF _(pos) −RF _(neg))×(LO ⁰ −LO ¹⁸⁰)×A1e ^(jP2) +DC2  Equation23State 4: (RF _(pos) −RF _(neg))×(LO ⁰ −LO ¹⁸⁰)×A1e ^(jP2) +DC2  Equation24State 1: (RF _(pos) −RF _(neg))×(LO ⁹⁰ −LO ²⁷⁰)×A1e ^(jP2)+DC2  Equation 25State 2: (RF _(pos) −RF _(neg))×(LO ⁹⁰ −LO ²⁷⁰)×A1e ^(jP2)+DC2  Equation 26State 3: (RF _(pos) −RF _(neg))×(LO ⁹⁰ −LO ²⁷⁰)×A1e ^(jP1)+DC1  Equation 27State 4: (RF _(pos) −RF _(neg))×(LO ⁹⁰ −LO ²⁷⁰)×A1e ^(jP1)+DC1  Equation 28

A higher-order delta-sigma modulator 321 running off a clock 322 higherthan the RF signal 300 modulation bandwidth is used to choose the LOPIand BBDI state. The delta-sigma modulator 321 generates a pseudo-randomnumber from 1 to 4. As an example, a Bluetooth™ signal's bandwidth is 1MHz, thus the interleaving may occur faster than 1 MHz such as 10 MHz.To continue the example, the delta-sigma pseudo random number modulator321 would generate 1.0 million random numbers per second; these numbersgenerated from the set 1, 2, 3 and 4. Delta-sigma pseudo random numbersforce the switching noise to higher frequencies. As an option, thenumbers may be completely random.

For the in-phase signal component, the DC offset has 4 values DC1,—DC1,DC2,—DC2 corresponding to states 1, 2, 3, 4 respectively. Likewise thequadrature baseband signal has 4 DC offset values each corresponding toa different interleaving combination. The amplitude and phase imbalancedistortion has two values for the in-phase baseband signal: A1e^(jP1)for states 1 and 2 and A2e^(jP2) for states 3 and 4. The quadraturebaseband signal follows the opposite pattern for amplitude and phaseimbalance.

Since a low pass filter can be interpreted as a time averaging function,the DC offset introduced by the mixers is averaged out in the basebandsignals. With equal numbers of switching matrix states occurring, the DCoffset is removed. This is summarized in the Equation 29.DC _(M1) −DC _(M1) +DC _(M2) −DC _(M2)=0  Equation 29

Similarly, the in-phase and quadrature baseband signal imbalancesaverage to the same value denoted in Equations 30 and 31.BB _(I) =RF×LO _(I)×(A1e ^(jP1) +A1e ^(jP1) +A2e ^(jP2) +A2e^(jP2))  Equation 30BB _(Q) =RF×LO _(Q)×(A1e ^(jP1) +A1e ^(jP1) +A2e ^(jP2) +A2e^(jP2))  Equation 31

So while the amplitude and phase distortion are still present in the Iand Q baseband signals, the distortion is now equal in the I and Qbaseband signals. Since the signals are balanced, the amplitude andphase distortion does not degrade the system performance. With only theaddition of a complex multiplicative term, Equations 30 and 31 areidentical to Equations 1 and 2 which are the expressions for an idealdirect-conversion receiver.

The present technology thus provides a solution for important drawbacksof a direct-conversion receiver: DC offset and quadrature imbalance.

FIG. 6 is an illustration of a multi-mode wireless communication systemin which one embodiment may be used. It should be understood that thecomponents shown in FIG. 6 are merely representative of one mode ofwireless communication system and that other communication systems mayuse different components in order to achieve similar, or even differentresults. For example, a wired transceiver communication system may alsobe employed. The claims, therefore, are not intended to be limited tothe system shown in FIG. 6. For example, the present technology may beimplemented in a single-mode system.

In the wireless communication system of FIG. 6, multi-mode, wirelesscommunication devices, otherwise referred to herein simply as wirelesscommunication devices, are shown as wireless communication devices 100a, 100 b, and 100 n, one or more wireless communication devices beingassigned to each user in the system. The designations a, b, and n on thewireless communication device identifiers correspond respectively to afirst user, a second user, and an nth user, representing “n” number ofusers in the communication system. Although only three wirelesscommunication devices 100 are shown in FIG. 6, it should be understoodthat a wireless communication system typically comprises many thousandsof users.

Referring again to FIG. 6, control station 120 typically includesinterface and processing circuitry for providing system control to basestations 110 a through 110 n, representing one through “n” base stationscomprising the wireless communication system. Base stations are providedfor transmitting and receiving communication signals to and fromwireless communication devices. Each base station 110 provides acoverage area ranging up to several miles in radius from the basestation location. As wireless communication devices travel within thecoverage area of each base station, communication signals to betransferred to and from the wireless communication device are routedgenerally through the particular base station to which the wirelesscommunication device is most closely located.

Control station 120 provides circuitry for routing communicationsbetween wireless communication devices operating in various base stationcoverage areas, as well as between remote stations and land-linetelephone users through a Public Switch Telephone. Network, shown inFIG. 6 as the PSTN 130. Control station 120 may, alternatively, or inaddition to, be connected to computer network 160 to providecommunications between wireless communication devices in thecommunication system and various known computing devices connected tocomputer network 160, such as personal computers, mainframe computers,digital cameras, email systems, remotely controlled devices, and so on.

Control station 120 typically comprises a telecommunications switch (notshown) and a Base Station Controller (BSC) (also not shown). Thetelecommunication switch provides a switching interface to PSTN 130while the BSC provides the necessary hardware and software forcommunications to take place between base stations. Control station 120provides other functions in the communication system as well, such asbilling services and data services.

Control station 120 may be coupled to the base stations by various meanssuch as dedicated telephone lines, optical fiber links, or microwavecommunication links. When a call is initiated by a wirelesscommunication device, a paging message is transmitted to one or morebase stations proximate to the wireless communication device initiatingthe call, generally over a paging channel. The paging message is routedto control station 120, where it is processed and routed either to PSTN130 or to one or more base stations proximate to a wirelesscommunication device for which the call is intended. When a call isinitiated from PSTN 130, a paging message is received by control station120 where it is then converted into a format suitable for the particularwireless communication system.

In the exemplary embodiment, the wireless communication device 100 isable to communicate in at least two modes, or types, of communications,data communications and voice communications. Data communication mode isused when it is desirous to send or receive information generallysuitable for digital computational devices, such as laptop computers.Data is generally transmitted in discreet segments called packets. Eachdata packet generally contains overhead information used for a varietyof purposes. For example, many data packets contain a data field used tostore an error detection code. The error detection code may be used tocheck a received data packet to ensure that it was received intact; thatis, the data was not corrupted during the transmission process.

Voice communication mode is used when it is desirous to transmitacoustic information, including human speech, facsimile tones, music, orother audible forms of communication. In voice communication mode, audioinformation is transmitted using one or more well-known wirelesscommunication modulation techniques, such as CDMA, TDMA, AMPS, andothers.

During typical voice communications, an over the air channel isestablished between one or more base stations and a wireless telephone.The channel is maintained throughout the duration of the voice call, nomatter how much or little voice activity is occurring between thewireless telephone and the base station. In many instances, voice datais digitized and formatted into packets prior to transmission. Voicepackets differ from data packets in that no information as to adestination address is contained within the voice packets. That is, aconnection is first established between two locations, then voice datais transmitted between the two locations. No address information need becontained within the voice packets as the source and destination of thevoice packets are predetermined by the connection.

Data mode may further include a capability of transmitting voice incertain applications. In this scenario, voice is digitized usingtechniques well known in the art. The digitized voice signals may beencrypted to provide for secure voice transmissions over the air. Thedigitized voice signals are then formatted into data packets, which arethen transmitted over the air using well-known data transmissionprotocols. As explained above, each data packet contains information asto the address, or destination, of where the data packet is to arrive.

FIG. 7 illustrates the functional components of a wireless communicationdevice, or wireless communication device, 100, shown in block diagramformat. It should be understood that the components shown in FIG. 7 aremerely representative of one mode of wireless communication device andthat other communication devices may use different components in orderto achieve similar, or even different results. The claims, therefore,are not intended to be limited to the system shown in FIG. 7.

Wireless communication device 100 is capable of multi-modecommunications, meaning that it can operate in several modes ofcommunications, such as voice communications or data communications. Itshould be understood that voice communications comprise any audioinformation including speech, music, or audible tones used for callprocessing, modems, and facsimile machines. Data communications comprisesynchronous or asynchronous data transmission. In addition to thesemodes, wireless communication device is also capable of other modes ofcommunications as well.

A user of wireless communication device 100 initiates communicationsgenerally by using input device 200. Input device 200 comprises a keypadin the exemplary embodiment, however, input device 200 could be anydevice which accepts user commands, such as a voice response devicewhich converts voice commands into electrical signals suitable forprocessing by controller 202. During voice communications, the userspeaks into microphone 204, which transforms acoustic energy intoelectrical energy and sends the electrical signals to controller 202 forprocessing.

Microphone 204 may be substituted for input device 200 in an applicationwhere a second audio input device is undesirable. In many instances, avoice encoder/decoder, generally known as a Codec, is used betweenmicrophone 204 and controller 202, or is incorporated within controller202, to convert the electrical signals from microphone 204 into a formatmore suitable for transmission over a limited bandwidth air interface.

Speaker 206 is used to convert received electrical signals into acousticsignals. Speaker 206 may comprise a speaker suitable for low volumeacoustic outputs, typically for use in a traditional telephoneapplication, or speaker 206 may comprise a loudspeaker, suitable forhigh volume acoustic outputs, typically for use in a dispatchapplications. In another embodiment, speaker 206 may comprise acombination of the high volume and low volume acoustic speakers.

Wireless communication device 100 further comprises display 208 forallowing a user to view operational characteristics of the wirelesscommunication device. Such displays are common in many of today'swireless devices including telephones and remote data terminals.

Data port 210 serves as an interface between controller 202 and externalhardware devices. Data port 210 generally allows a variety ofbi-directional data communications to take place between wirelesscommunication device 100 and the external device. Such external devicesinclude laptop computers, facsimile machines, and remote data terminals,among others.

When a user initiates voice or data communications, an identificationcode corresponding to a second communication device, generally atelephone number, is entered using input device 200. In the exemplaryembodiment, input device 200 comprises keys corresponding to digits 0through 9, as well as additional function keys, such as SEND, END, andso forth. Input device 200 may also comprise one or more keys used toclassify an outgoing communication as being a data communication or avoice communication.

For example, a user wishing to initiate a data communication might pressa key designated for data communications, then dial a telephone numbercorresponding to a data device that the user wishes to communicate with.In one embodiment, all calls from wireless communication device 100 areassumed to be voice calls, unless classified as some other mode ofcommunication, as described by one of the methods above.

Controller 202 serves as the main computational unit of wirelesscommunication device 100. Although controller 202 is shown as a singleelement in FIG. 7, it should be understood that controller 202 maycomprise one or more individual components such as one or moreApplication Specific Integrated Circuits (ASICs) in combination withmemory devices, bus controllers, and other support devices well known tothose skilled in the art.

To facilitate the transmission and receipt of wireless RF signals in theforegoing context, an RF transceiver 212 and an antenna 214 are coupledto controller 202 for sending and receiving such signals. Similar to thecontroller 202, one or more ASICs in combination with memory devices,bus controllers, etc. may be used to provide the RF transceiver 212.Moreover, the aforementioned direct-conversion receiver may beincorporated into the RF transceiver 212 and/or controller 202 in anydesired capacity for providing an improved system.

Working in conjunction with the controller 202 is memory 216. The memory216 is a device used to store information represented in digital format.Examples of memory 216 include random access memory (RAM), electricallyerasable programmable read-only memory (EEPROM), non-volatile memory,and other known storage devices.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

1. A method of processing a signal, the method comprising: receiving thesignal; and mixing the signal with a first phase interleaved LocalOscillator (LO) signal to generate a frequency downconverted first phaseinterleaved signal, the downconverted first phase interleaved signalinterleaving at least downconverted in-phase and quadrature signals. 2.The method of claim 1, further comprising mixing the signal with asecond phase interleaved LO signal to generate a second phaseinterleaved baseband signal.
 3. The method of claim 2, furthercomprising maintaining a phase offset of the first phase interleaved LOsignal relative to the second phase interleaved LO signal.
 4. The methodof claim 1, wherein the signal comprises a modulated Radio Frequency(RF) signal.
 5. The method of claim 1, wherein the frequencydownconverted first phase interleaved signal comprises a first phaseinterleaved baseband signal.
 6. The method of claim 1, wherein the firstphase interleaved LO signal comprises interleaved in-phase LO signal andquadrature LO signal.
 7. The method of claim 1, wherein the first phaseinterleaved LO signal comprises a LO signal phase interleaving 0, 90,180, and 270 degree LO signals.
 8. The method of claim 1, wherein thefirst phase interleaved LO signal comprises a plurality of LO phasesinterleaved in a pseudorandom order.
 9. The method of claim 1, whereinthe first phase interleaved LO signal comprises a plurality of LO phasesinterleaved a rate greater than a signal bandwidth.
 10. The method ofclaim 1, wherein generating the phase interleaved LO signal comprises:generating a LO signal; generating a plurality of phases of the LOsignal; and interleaving the plurality of phases of the LO signal.
 11. Amethod of processing a modulated radio-frequency (RF) signal, the methodcomprising: receiving the modulated RF signal; and mixing the modulatedRF signal with a plurality of phase interleaved LO signals to generate aplurality of in-phase and quadrature interleaved baseband signals. 12.The method of claim 11, wherein receiving the modulated RF signalcomprises: receiving a single-ended modulated RF signal; and generatinga differential modulated RF signal.
 13. The method of claim 11, whereinmixing the modulated RF signal comprises: mixing the modulated signalwith a first phase interleaved LO signal to generate a first interleavedbaseband signal; and mixing the modulated signal with a second phaseinterleaved LO signal to generate a second interleaved baseband signal,wherein the second phase interleaved signal is in quadrature with thefirst phase interleaved LO signal.
 14. The method of claim 1, whereinmixing with the plurality of phase interleaved LO signals comprisesmixing with the plurality of phase interleaved LO signals comprisinginterleaved 0, 90, 180, and 270 degree LO signals.
 15. The method ofclaim 11, further comprising deinterleaving the plurality of in-phaseand quadrature interleaved baseband signals to generate an in-phasebaseband signal and a quadrature baseband signal.
 16. The method ofclaim 15, wherein deinteleaving the plurality of in-phase and quadratureinterleaved baseband signals comprises: selectively coupling a firstin-phase and quadrature interleaved baseband signal to an in-phasebaseband signal path based at least in part on a phase of a first of theplurality of phase interleaved LO signals; and selectively coupling asecond in-phase and quadrature interleaved baseband signal to thein-phase baseband signal path based at least in part on a phase of asecond of the plurality of phase interleaved LO signals.
 17. The methodof claim 15, wherein deinteleaving the plurality of in-phase andquadrature interleaved baseband signals comprises selectively invertingeach of the plurality of in-phase and quadrature interleaved basebandsignals based at least in part on a phase of a corresponding one of theplurality of phase interleaved LO signals.
 18. A method of processing asignal, the method comprising: generating first and second interleavedsignals from a received RF signal, wherein each of the first and secondinterleaved signals interleaves in-phase and quadrature periods; anddeinterleaving the first and second interleaved signals to generatein-phase and quadrature signals.
 19. The method of claim 18, whereingenerating first and second interleaved signals comprises: mixing thereceived RF signal with a first interleaved LO signal to generate thefirst interleaved baseband signal; and mixing the received RF signalwith a second interleaved LO signal to generate the second interleavedbaseband signal, wherein the second interleaved LO signal is inquadrature with the first phase interleaved LO signal.
 20. The method ofclaim 18, wherein deinterleaving the first and second interleavedsignals comprises selectively inverting the first and second interleavedsignals.
 21. The method of claim 18, wherein deinterleaving the firstand second interleaved signals comprises selectively routing the secondinterleaved signal to an in-phase signal path.
 22. The method of claim21, wherein deinterleaving the first and second interleaved signalsfurther comprises concurrently routing the first interleaved signal to aquadrature signal path when the second interleaved signal is routed tothe in-phase signal path.
 23. An apparatus for processing an inputsignal, the apparatus comprising: a Local Oscillator (LO) subsystemconfigured to generate a first interleaved LO signal having in-phase andquadrature states; a first mixer configured to mix the input signal withthe first interleaved LO signal to generate a first interleaved basebandsignal; and a second mixer configured to mix the input signal with asecond interleaved LO signal that is in quadrature with the firstinterleaved LO signal to generate a second interleaved baseband signal.24. The apparatus of claim 23, wherein the LO subsystem comprises: a LOconfigured to generate an LO signal; a polyphase network coupled to theLO and configured to generate a plurality of phase offset LO signals,each of the plurality of phase offset LO signals at a different phaseoffset relative to the LO signal; and an interleaver coupled to thepolyphase network and configured to select one of the plurality of phaseoffset LO signals for each of the states of the first interleaved LOsignal.
 25. The apparatus of claim 24, wherein the plurality of phaseoffset LO signals comprise phase offsets of 0, 90, 180, and 270 degrees.26. The apparatus of claim 24, wherein the interleaver is furtherconfigured to select for the second interleaved LO signal a phase offsetthat is in quadrature to the phase offset selected for the state of thefirst interleaved LO signal.
 27. The apparatus of claim 23, wherein thefirst interleaved LO signal comprises 0, 90, 180, and 270 degree phaseoffset states.
 28. The apparatus of claim 23, further comprising aninterleaving clock configured to control an update rate of the states ofthe first interleaved LO signal.
 29. The apparatus of claim 28, whereinthe interleaving clock operates at a rate higher than a modulationbandwidth of the input signal.
 30. The apparatus of claim 28, furthercomprising a delta-sigma modulator coupled to the interleaving clock andconfigured to generate a pseudorandom number used to determine the stateof the first interleaved LO signal.
 31. The apparatus of claim 23,further comprising a deinterleaver coupled to the first mixer and thesecond mixer and configured to deinteleave the first and second basebandsignals to generate an in-phase baseband signal and a quadraturebaseband signal.
 32. The apparatus of claim 31, further comprising: aninterleaving clock configured to control an update rate of the states ofthe first interleaved LO signal; and a delta-sigma modulator coupled tothe interleaving clock and configured to generate a pseudorandom numberused to determine the state of the first interleaved LO signal, andwherein the deinterleaver deinterleaves the first and second basebandsignals based at least in part on the state of the first interleaved LOsignal.
 33. The apparatus of claim 23, further comprising adeinterleaver coupled to the first mixer and configured to selectivelyswitch the first interleaved baseband signal to one of an in-phasesignal path or a quadrature signal path, based on the state of the firstinterleaved LO signal.
 34. An apparatus for processing an input signal,the apparatus comprising: a LO configured to generate an LO signal; apolyphase network coupled to the LO and configured to generate aplurality of phase offset LO signals, each of the plurality of phaseoffset LO signals at a different phase offset relative to the LO signal;an interleaver coupled to the polyphase network and configured to selectone of the plurality of phase offset LO signals for each of a pluralityof states of a first interleaved LO signal, and further configured toselect one of the plurality of phase offset LO signals for each of aplurality of states of a second interleaved LO signal, such that thesecond interleaved LO signal is in quadrature to the first interleavedLO signal; a first mixer configured to mix a modulated Radio Frequency(RF) signal with the first interleaved LO signal to generate a firstinterleaved baseband signal; a second mixer configured to mix themodulated RF signal with the second interleaved LO signal to generate asecond interleaved baseband signal; and a deinterleaver coupled to thefirst mixer and the second mixer, and configured to selectively switchthe first interleaved baseband signal to one of an in-phase signal pathor a quadrature signal path, based on the state of the first interleavedLO signal, and further configured to selectively switch the secondinterleaved baseband signal to one of the in-phase signal path or thequadrature signal path, based on the state of the second interleaved LOsignal.
 35. An apparatus for processing an input signal, the apparatuscomprising: means for receiving a modulated Radio Frequency (RF) signal;and means for mixing the modulated RF signal with a plurality of phaseinterleaved LO signals to generate a plurality of in-phase andquadrature interleaved baseband signals.
 36. The apparatus of claim 35,further comprising means for deinterleaving the plurality of in-phaseand quadrature interleaved baseband signals coupled to the means formixing the modulated RF signal, and configured to generate an in-phasebaseband signal and a quadrature baseband signal.
 37. The apparatus ofclaim 36, wherein the means for deinterleaving the plurality of in-phaseand quadrature interleaved baseband signals comprises: means forselectively coupling a first in-phase and quadrature interleavedbaseband signal to an in-phase baseband signal path based at least inpart on a state of a first of the plurality of phase interleaved LOsignals; and means for selectively coupling a second in-phase andquadrature interleaved baseband signal to the in-phase baseband signalpath based at least in part on a state of a second of the plurality ofphase interleaved LO signals.
 38. The apparatus of claim 35, furthercomprising means for generating the plurality of phase interleaved LOsignals.